The invention relates to a method to determine a numerical percentage value as a diagnostic indicator of the blood sugar condition of a specific person. The invention also relates to an improved liquid chromatographic column for practice of the method.
According to the invention, a whole blood sample is collected from the person or patient and thereafter prepared as a red blood cell hemolysate test sample using alternative clinical chemistry techniques and procedures. Thereafter, the invention provides a series of steps for separating, detecting and measuring the amount of a group of hemoglobin species present in the test sample using improved ion exchange cellulose liquid column microchromatographic apparatus, techniques and procedures, spectrometric analysis, and mathematical computation.
In biochemistry, hemoglobins are the amphoteric protein molecule coloring matter of the red blood corpuscles serving to convey oxygen to the tissues. Several chromatographically separable minor hemoglobins are present in red blood cell hemolystates of normal persons. Some minor hemoglobins are designated as Hb-A.sub.1a, Hb-A.sub.1b, Hb-A.sub.1c, Hb-A.sub.1d, and Hb-A.sub.1e. The hemoglobin species Hb-A.sub.1c is most prominent and accounts for the major portion of the minor hemoglobins. It is known that the level of hemoglobin Hb-A.sub.1c has been related to a patient's average blood sugar level. Normal persons are expected to have 3-6% Hb-A.sub.1c relative to their total hemoglobin. Untreated diabetics may have 6-12% Hb-A.sub.1c relative to their total hemoglobin, whether the affliction is of the juvenile-onset or adult-onset type. Still further, it is understood that the levels of the species Hb-A.sub.1a-c, as a separate and identifiable sub-group, may serve as an indicator of the degree of hyperglycemia, an excess of sugar in the blood, over a prolonged period of time.
Prior literature relating to the diagnosis of abnormal blood sugar (diabetes mellitus) by determination and measurement of the level of the hemoglobin species Hb-A.sub.1c includes: (i) The Relation Between the Minor Components of Whole Normal Human Adult Hemoglobin as Isolated by Chromatography and Starch Block Electorphoresis, Schnek and Schroeder, Journal of the American Chemical Society, Vol. 83, pp. 1472-1478, March 1961; (ii) Hemoglobin Components in Patients with Diabetes Mellitus, Trivelli, et al, New England Journal of Medicine, Vol. 84, pp. 353-357, February 1971; (iii) The Biosynthesis of Human Hemoglobin A.sub.1c, Bunn, et al, Journal of Clinical Investigation, Vol. 57, pp. 1652-1659, June 1976; (iv) Correlation of Glucose Regulation And Hemoglobin A.sub.1c in Diabetes Mellitus, Koenig, et al, New England Journal of Medicine, Vol. 295, pp. 417-420, August 1976; (v) Red Cell Age-Related Changes of Hemoglobins A.sub.1a+b and A.sub.1c in Normal and Diabetic Subjects, Fitzgibbons, et al, Journal of Clinical Investigation, Vol. 58, pp. 820-824, October 1976; (vi) Glycosylated Hemoglobins and Long-Term Blood Glucose Control in Diabetes Mellitus, Gabbay, et al, Journal of Clinical Endocrinology and Metabolism, Vol. 44, pp. 859-864, 1977; and, (vii) Rapid Estimation (21/2 Hours) of Glycosylated Hemoglobin For Routine Purposes, Kynoch and Lehmann, The Lancet, p. 16, July 1977.
Until now, the clinical techniques and procedures for determination of the level of the hemoglobin species Hb-A.sub.1c have had the disadvantage of requiring elaborate equipment and a testing time space of several hours or even days. It has now been found possible, according to the invention, to determine, as a numerical percentage value, the ratio of the sub-group of hemoglobin species Hb-A.sub.1a-c to the total hemoglobins (Hb) quickly, inexpensively and accurately. Such a numerical percentage value is available for use as a diagnostic indicator of the blood sugar characteristics of the suspected diabetic.